COMBINING ABILITY FOR SEED YIELD AND OTHER CHARACTERS IN RAPESEED

Rapeseed (Brassica napus L.) is one of the most important oilseed crops of China. The improvement of yield and oil content is presently being emphasized for this crop. The objective of this study was to evaluate combining ability of rapeseed lines to be used in breeding for yield, oil content and other characters. Nine inbred lines used as males were crossed to five recessive genetic male sterile (RGMS) lines used as females in a factorial manner (NCII design) to produce 45 single crosses. The crosses and their parents were tested at Guiyang and Zunyi, Guizhou, China in 2007-2008. The results showed that mean squares for hybrids were significantly different for all characters. The SS ratios of sum of squares due to GCA to sum of squares of hybrids were 0.70, 0.80, 0.88 and 0.82 for seed yield, oil content, days to flowering and days to maturity, respectively, but SCA effects were significant for all characters except for days to maturity. This indicates that both additive and non-additive gene effects were important, but additive gene effects were more predominant for these characters. Males III188, III224, and Q034 gave large positive GCA effects for seed yield. Their respective values were 317.6, 253.1, and 383.5 kg ha(-1). Significantly positive GCA effects for oil content were detected for lines III224 and QH303-4A of which the respective GCA effects were 0.66 and 2.31%. The crosses of Qianyou 8A x Q034, QH303-4A x III224, Qianyou 3A x 2365, QH303-4A x 1190, and 24A x III153 gave significant postitive SCA effects of 434.6, 429.9, 427.8, 379.4, and 347.0 kg ha(-1) for seed yield, respectively. Therefore, they should be considered as candidates for future hybrid breeding program.